1. Field of the Invention
The present invention relates to antibacterial mixtures comprising 2-alkylimidazolines wherein the alkyl group has about 9 to about 17 carbon atoms, and a bacteriostat. Preferably the bacteriostat is a compound selected from the group consisting of 3,4',5-tribromosalicylanilide 4',5-dibromosalicylanilide, or 2,4,4'-trichloro-2'-hydroxydiphenyl ether, or mixtures thereof. The compound 3,4',5-tribromosalicylanilide is referred to in portions of this specification as TBS; 4',5-dibromosalicylanilide is DBS, and 2,4,4'-trichloro-2'-hydroxydiphenyl ether is THDE.
The antibacterial mixtures have utilized for a variety of applications, such as sanitizing of walls and floors, as germicidal agents in toilet bars or in dishwashing compositions, and are especially useful in the washing of fabrics.
The components of the antibacterial mixtures of the present invention have the following structural formulas: ##STR1## wherein R is an alkyl group having 9-17 carbon atoms.
It will be understood that the imidazolines referred to herein are the 2-substituted-2-imidazolines in accordance with the foregoing structure.
Numerous classes of bacteria survive automatic home laundry washing operations. Gram-negative bacteria have been found on washed clothes although these bacteria are largely destroyed when the clothes are dried. The Gram-positive bacteria, being more resistant to drying, are more frequently found on washed clothes than are the Gram-negatives. One of the more important Gram-positive bacteria, from the standpoint of public health, which has been found to persist on washed and dried clothes is Staphylococcus aureus. The antibacterial mixtures of the present invention are highly effective against the growth of this organism.
The need for eliminating bacteria on washed clothes or at least reducing bacteria to a minimum level is apparent. Formerly clothers were sanitized, i.e., bacteria reduced to a minimum level, by boiling in the wash operation. This procedure however does not impart bacteriostatic properties to the washed clothes, nor is it recommended for the case of present day synthetic or Permanent Press fabrics.
The word "sanitize" as used herein relates to the reduction of the number of bacteria on a fabric or other object to minimum levels as may as judged by public health requirements. The percent reduction may vary somewhat but generally is within the range of 95% to 99.999%, as set forth under "sanitizer" on page 7 of the booklet "Anti-Microbial Agents" (Interpretive Report) published by the Chemical Specialties Manufacturers Association, New York.
The present day practice of washing clothes in automatic washers is less effective for reducing bacterial level than the boiling method. The "hot water" setting seldom provides wash water having a temperature as high as 140.degree. F. in any washing machine, and in view of the fact that it requires about 20 minutes to kill staphylococci by heat alone at 140.degree. F. (the average home washing cycle is about 10 minutes) the usual washing operation cannot be expected to provide a sanitizing action. Also, some commercial detergent compositions are currently being formulated to wash in water at room temperature, which is usually about 68.degree. F. to about 85.degree. F. (about 20.degree. C. to about 30.degree. C.), and under these conditions the need for antibacterial action in the washing or rinsing operation is accentuated. Highly desirable too is a bacteriostatic action to lessen recontamination. Accordingly it has not been possible heretofore to sanitize clothing in a washing machine operation without resorting to the use of such antibacterial agents as quaternaries, hypochlorites, phenolics, or pine oil, or the use of relatively high levels of the organic halogen-containing antibacterial agents.
There are recognized drawbacks to the use of any of the above agents. Hypochlorites should not be used on silk or wool, and may bleach colored fabrics. Quaternaries are inactivated when used in the wash cycle with anionic detergents, while the phenolics and pine oil have odors that may be objectionable to some people. The high levels of the organic halogen-containing antibacterials which have been needed heretofore for both bactericidal and bacteriostatic action precluded their use on the basis of cost.
For a discussion of the bacterial problems encountered in home laundering, attention is directed to the seven-page brochure "Sanitation in Home Laundering" (Revised August, 1964) published by the United States Department of Agriculture, and available from the Superintendent of Documents.
2. The Prior Art
The desirability of incorporating a germicidal agent in detergent compositions has long been recognized, and much that has been written on the subject is found in the technical journals and in the patent literature. None of these however discloses the accomplishment set forth in the instant invention, i.e., the sanitizing of clothes in a single wash, even at relatively low temperatures, i.e., about 20.degree. C. to about 40.degree. C. Typical prior-art disclosures are discussed below.
Belgium Pat. No. 575,411, based on an application filed in the United States on Feb. 6, 1958, discloses the use of 0.01% to 2% of 3,3',4',5-tetrachlorosalicylanilide or related compounds, and additionally trichlorocarbanilide, and tetramethyl thiuram disulfide, as antibacterial agents in detergent compositions, useful at washing temperatures of 49.degree. C.
Somewhat later the use of 1-hydroxy-2-pyridinethione compounds in detergent compositions was disclosed in South Africa Patent Application No. R61/1706 dated Sept. 26, 1961.
U.S. Pat. No. 3,428,736 issued on Feb. 18, 1969 describes synergistic bactericidal combinations comprising bis(3,5,6-trichloro-2-hydroxyphenyl)mothane (hexachlorophene) and a dibenz[be][1,4] oxiodinium salt, suitable for use in detergent compositions.
British Pat. No. 727,343 published in 1955 discloses and claims a broad group of halogenated salicylanilide compounds, and states that these compounds can be used with cleaning agents and other vehicles, for disinfectant purposes.
British Pat. No. 955,925, published in 1964 discloses that textile fibers can be made resistant to the growth of bacteria by washing the textile fibers with a detergent in which has been incorporated a mixture of 3,4',5-tribromosalicylanilide and one or more dibromosalicylanilides.
South Africa Pat. No. 68/3304 discloses that certain benzimidazoles retain their antimicrobial activity when added to cleaning agents.
The present invention permits substantially complete reduction in Staphylococcus aureus count on textile fabrics in one wash at room temperature or slightly higher, with residual antibacterial protection for extended periods. Prior art antimicrobial agents or mixtures thereof generally require elevated washing temperatures to obtain sanitizing and residual action. A typical teaching in this respect is found in British Pat. No. 955,925, which discloses a washing temperature of 49.degree. C. (120.degree. F.). Thus the present invention is timely, since it provides a means for obtaining good sanitizing and residual antimicrobial action in relatively cool water in conformity with the current practice of using room-temperature water in home laundering operations.
Typical also of prior washing conditions is the teaching of U.S. Pat. No. 3,211,607, wherein (in Example 4) there is described a washing test made at 40.degree. C. and of 18 minutes' duration, using about 8%, basis detergent composition, (or 200 ppm, basis washing liquor) of a synergistic binary mixture of an amino imidazolidine and a trifluoromethyl dichlorocarbanilide. It is noteworthy that this mixture was tested at a longer contact time and at a much higher level of antibacterial mixture to obtain bactericidal action only, than required for the antibacterial mixture of the present invention to achieve both bactericidal and bacteriostatic activity.